Disposable surgical mask

ABSTRACT

This improvement in surgical masks provides a tissue barrier layer or ply between the filter and the inner ply facing of a disposable surgical mask for the purpose of stopping spicules from the filter from working their way through the inner facing ply, and to add some stiffness to the mask so that the mask has less tendency to collapse when the wearer inhales. The barrier tissue adds wet strength to the mask for protection against breakdown of the non-woven inner ply when moistened by the breadth of the wearer; and the added stiffness provided by the barrier ply also reduces the flexing of the filter which causes increase in the number of spicules which become detached from the filter.

United States Patent 1191 Lutz et a1.

1 1 DISPOSABLE SURGICAL MASK [75] Inventors: William A. Lutz; FrederickW. Zipf,

111, both of Ru'mson, NJ.

[73] Assignee: Blessings Products, Incorporated,

Bound Brook, NJ.

[22] Filed: Jan. 29, 1973 [21] Appl. No.: 327,311

52 US. Cl. 128/1462 51 1111.0. A61M 15/00 58 Field 61 Search 128/1462,146.6, 146,

[56] References Cited UNITED STATES PATENTS 3,603,315- 9/1971 Becker128/1462 3,613,678 10/1971 Mayhew 128/1462 3,664,335 5/1972 Boucher128/1466 Primary Examiner-Richard A. Gaudet Assistant Examiner-Henry J.Recla Attorney, Agent, or Firm-Sandoe, H opgood & Calimafde [57]ABSTRACT This improvement in surgical masks provides a tissue barrierlayer or ply between the filter and the inner ply facing of a disposablesurgical mask for the purpose of stopping spicules from the filter fromworking their way through the inner facing ply, and to add somestiffness to the mask so that the mask has less tendency to collapsewhen the wearer inhales. The barrier tissue adds wet strength' to themask for protection against breakdown of the non-woven inner ply whenmoistened by the breadth of the wearer; and the added stiffness providedby the barrier ply also reduces the flexing of the filter which causesincrease in the number of spicules which become detached from thefilter.

7 Claims, 4 Drawing Figures DISPOSABLE SURGICAL MASK BACKGROUND ANDSUMMARY OF THE INVENTION The typical disposable surgical mask iscomposed of three basic parts: inner and outer facings of non-wovenfabrics or similar material between which is sandwiched the filter mediaof micro-fibre glass. To these, of course, the various bindings, ties,etc. are attached to form the mask.

The micro-fibre glass media can and does cause irritation to the face ofthe wearer as a result of the abrading action of tiny spicules of glassworking their way through the inner facing of the mask. While theirritation is superficial and transitory, it is a serious annoyance toall users of micro glass filter masks, and the same could be true ofmasks using other fibres for the filter.

None of the commonly used inner facing materials offer adequateprotection against glass strike-thru. The mask of this invention uses afourth ply or barrier between the inner facing and the filter media. Atissue with certain characteristics best meets the needs.

The barrier must be light in weight so as not to add noticeably to theweight of the mask. It has to be strong enough to resist the penetrationof the glass spicules and to have a density and porosity suitable forthis purpose. The barrier ply must, however, have high enough porosityso that breathability of the mask is not noticeably diminished and itmust have a wet strength that resists breakdown from moisture resultingfrom the breath of the wearer.

Other objects, features and advantages of the invention will appear orbe pointed out as the description proceeds.

BRIEF DESCRIPTION OF DRAWING In the drawing, forming a part hereof, inwhich like reference characters indicate corresponding parts in all theviews:

FIG. 1 is a front view, partly broken away and in section, of a surgicalmask made in accordance with this invention;

FIG. 2 is a sectional view taken on the line 22 of FIG. 1;

FIG. 3 is a view showing the mask of FIG. 1 with the pleats extended asthey are when the mask is worn by a user of the mask; and

FIG. 4 is a greatly enlarged sectional view taken on the line 4-4 ofFIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 shows a surgical mask 10which is formed of four plies of material. The first ply is an outerfacing 12, preferably formed of non-woven fabric. The second ply is afilter 14 made of micro-fibre glass.

The third ply is a barrier tissue 16 for preventing spicules of glassfrom the filter 14 from reaching an inner facing 18 which comprises thefourth ply of the mask.

The plies 12-18 are secured together at their top edges 20 by binding 22which is folded over the top edges 20; and the binding 22 is secured tothe plies 12-18 by stitching 24. This stitching also holds the plies12-18 together at their upper ends. A similar binding 22 with stitching24 is applied bottom edge of the mask 10.

When the mask is in its folded or flat condition, all of the plies 12-18lie against one another and they are pleated as shown in FIG. 2. Becauseof the scale of the drawing in FIG. 2 it is not practical to attempt toshow the individual plies; and the assembly of the plies 12-18 isindicated in FIGS. 2 and 3 by the reference character 28. FIG. 2 showsthe way in which the assembly of plies 28 is pleated to form pleats 32and 34.

Referring again to FIG. 1 there is binding 36 folded over both the righthand and left hand edges of the plies 12-18; and this binding is securedto the plies 12-l8 by stitching 38. This stitching 38 holds the plieswith the pleats 32 and 34 folded along both sides of the mask. Thepleats can be opened up and the assembled plies 28 form into an arch atthe center portion of the mask. This arch flattens out toward both sidesof the mask but provides an arched center for space ahead of the wearersnose and to keep the mid portion of the mask out of contact with thewearers face. In accordance with conventional practice, there is amaleable metal strip 42 adhered to the front facing of the assembledplies 28. This metal strip is bent down manually around the wearers noseto cause the top of the mask to conform to the contour of the wearersface, thereby preventing the formation of large gaps between the top ofthe mask and the wearers face on opposite side of the wearers nose. Atthe bottom of the mask, the binding 22 will lie close to and in contactwith the wearers chin and checks when the bottom edge of the mask ispulled against the wearers face by straps 44 which are extensions of thebinding 36. The upper part of the mask is held against the wearers faceby other straps 46 which are also extensions of the binding 36. Thisconstruction is conventional and no furtherdescription of it isnecessary for a complete understanding of this invention.

FIG. 4 shows the assembled plies 28 on a greatly enlarged scale so thatthe individual plies can be shown in section. The outer facing 12 andthe inner facing 18 of the mask are preferably made of non-wovenmaterial such as cellulose with a porosity of at least 200, andpreferably approximately 500 cubic feet or more per minute per squarefoot (Gurley peromometer). The preferred embodiment of the invention hasthe outer facing 12 and the inner facing 18 made of cellulosic non-wovenfibers held together with a binder.

The filter 14 is of conventional construction. Such filter medium ismade exclusively from preselected and wet cleaned Vinyon and microglassfibers with less than 1.2% by weight of non-allergenic latex binder.These filters contain no cellulose or other natural materials. Typicalproperties are coverage 98 square feet per pound; thickness 0.0085 inchat 7 9 pounds per square inch (Tappi. method); tensile strength machinedirection, 225 grams per inch, cross-machine direction 150 grams perinch; permeability 60 cubic feet per minute per square foot at 0.5inches water; filtration efficiency minimum in accordance with militaryspecification M-3643IB. These specifications are given merely by way ofillustration.

Glass filters are almost universally used for disposable surgical maskseven though those glass filters have the objection that spicules ofglass become detached from the filter media and penetrates through theinner facing of the mask so that they contact with and irritate the skinon the face of the person wearing the mask. In spite of the irritatingeffect caused by the glass fiber filter media in disposable masks, theextremely effective filtering obtained from such glass fiber masks is somuch better than any other inexpensive filter medium known at thepresent time that glass filters continue to be used in spite of theobjection to them caused by the breaking off of spicules of glass.

Glass fiber filter media for face masks are available from C. H. DexterCo., Windsor Locks, Conn.; and Strathmore Paper Co., Westfield, Mass.

This invention is not limited to masks madewith the particular glassfilter media described above, but can be used with any mask which has aglass fiber filter media which presents the same problem of glassspicules penetrating an inner facing that contacts with the face of theperson wearing the mask.

The barrier tissue 16 is made of a special tissue which is commonlyreferred to in the trade as tea bag paper. This paper is extremely lightin weight; as low as seven pounds in basis weight, one commercial gradeis 7.25 pounds per 2,880 square feet. The light weight is obtainedwithout sacrifice of strength by making the paper with long fibers. Thelength of fibers is preferably approximately 5 to 6 millimeters and inany event more than 4 millimeters. These long fibers-add greatly to thestrength of the paper and lighter paper can be obtained by using hempfibers. The paper used for the barrier layer 16 is preferably made withat least 50% of its long fibers in excess of approximately fourmillimeters.

Tests show that such paper with long fibers has a strength about twiceas great as paper with short fibers. This strength is important inpreventing the glass spicules from working their way through the barrierply 16.

The porosity of the barrier layer 16 should not be less than 200 cubicper minute per square foot since lower porosity reduces thebreathability of the overall mask to an unacceptable limit. Thisporosity is necessary in order to offset the relatively low porosity ofthe glass fiber filter which is ordinarily only about 60 cubic feet perminute per square foot. The preferred embodiment of the invention uses abarrier sheet 16 having a porosity of approximately 550 cubic feet perminute per square foot.

In the preferred construction the strength of the paper used for thebarrier ply 16, by virtue of its long fibers, has approximately twicethe strength of wood pulp paper of the same weight, and a maximumporosity of about 800.

The paper used for the barrier ply 16 is a paper that is ordinarily madewith raw manila hemp which has a fiber length about twice that of woodfiber normally used in paper making. As previously explained, it is thefiber length that gives the unusually high strength to weight ratio anda porosity of the paper used for the barrier ply 16. The fibers of thispaper are usually combined with a resin such as poly-amide for wetstrength and binding. It is possible to use heat sealable fibers andresins in the sheet, but experiments indicate that this is not desirablefor the face mask barrier tissue 16.

Other fibers than manila hemp can be used in the construction of thepaper, such as rayon or sisal fibers, either separately or incombination with each other and with hemp, and some short fiber can beused, but the long fiber content of the paper should not be less than50%.

Tea bag paper" suitable for the barrier ply 16 can be purchased from theC. H. Dexter Co., Windsor Locks, Conn., and also from Peter J.Schwitzer, Divi- 4 sion of Kimberly-Clark Corporation, New York City,NY.

When a mask is worn for an extended period of time, the inner facing 18becomes soaked with moisture caused by the exhaling of the wearer of themask. This moisture accumulation, when it becomes excessive, causes theinner facing 18 to wet-out. This expression is used to designate acondition in which air can no longer pass through the inner facing andwith the result that the inner facing will pull apart unless there areadequate areas of dry facing 18 beyond the wetted area to permit readypassage of air each time the wearer exhales.

The barrier ply 16, being made of tissue paper, instead of non-wovenfabric, is somewhat stiffer than the non-woven fabric of the innerfacing 18 and thus adds stiffness to the ply assembly so that it willremain in an arched condition, as shown in FIG. 3, more effectively andthus maintain the arch holding it away from the wearers face even thoughthe breathability of the mask becomes somewhat impaired after extendeduse and as a result of moisture accumulation on the plies.

It is not satisfactory to omit the inner facing ply 18 and let thebarrier tissue 16 contact with the face of the wearer of the mask. Thebarrier tissue 16 is much rougher than the non-woven inner facing 18 sothat the omission of the inner facing 18 makes the mask uncomfortable towear.

The use of the combination of the barrier ply 16 with the inner facing18 seems to make the mask of this invention more effective in stoppingglass spicules. Experiments made with a plurality of layers of non-wovenfacing material 18 did not effectively stop glass spicules from workingthrough the mask and contacting with the face of the wearer. Otherexperiments with the inner facing ply 18 next to the glass fiber filter14 and with the barrier tissue 16 on the inside surface of the maskeffectively stopped the glass spicules but such a construction isunsatisfactory because of the roughness of the barrier tissue 16 ascompared to the inner nonwoven material of the inner facing 18. Theconstruction as shown in FIG. 4 is, therefore, the most effective and atthe same time the most comfortable construction for the mask.

The barrier tissue has a basis weight between 6.75 and 7.75 lbs. per2880 sq. ft. and preferably about 7.25 lbs. per 2880 sq. ft. Porosityhas been described above. Tensile strength is preferably about asfollows:

Dry oz./in. Machine direction 2825 Cross direction 970 Wet Machinedirection 580 Cross direction 200 i The lower limit for both dry and wetstrength is not less than 60% of these preferred values.

Tests made on the mask of this invention indicate that air for inhalingand exhaling by someone wearing the mask of this invention, passesthrough the mask more easily with the barrier layer in the mask thanwithout it (all other structure being the same). Applicant has not yetdiscovered the reason for this phenomena.

The preferred embodiment of this invention has been illustrated anddescribed but changes and modifications can be made and some featurescan be used in different combinations without departing from theinvention as defined in the claims.

What is claimed is:

l. A disposable surgical mask comprising pleated plies of sheet materialwith the pleats extending across the face of the mask, binding coveringthe pleats at their ends, stitching through the binding and pleatedmaterial securing the pleats closed at the ends of the mask, the pliesincluding inner and outer facings for the mask, a ply of filter materialbehind the front facing, the filter being made of material from whichspicules of the filter become loosened during use of the mask, and a plyof barrier material between the filter and the inner facing of aporosity that stops spiclues of the filter from reaching the innerfacing during use of the mask, and the barrier ply being made of tissuepaper having a porosity of from 200 to 800 cu. ft./min (GurleyPermometer), a basis weight between 7 and 10 lbs/2880 sq. ft. andcomprising at least 50% long fiber, and a wet strength of about 580(machine direction) and 200 (cross direction) gms./inch.

2. The disposable surgical mask described in claim 1 characterized bythe porosity being between 400 and 600 cu.ft./rn in.

3. The disposable surgical mask described in claim 1 characterized bythe pleats extending horizontally across the mask and having overlapsthat unfold to increase the vertical width of the mask at its midsection more than between 50 and of the vertical width when the pleatsare folded, and all of the plies being in contact with one another andsimilarly pleated.

4. The disposable surgical mask described in claim 3 characterized bythe barrier coat being made of tissue paper having a porosity between400 and 600 cu.ft/- min. and a wet strength above 290 (machinedirection) and 100 (cross direction) grams/inch, and having a basisweight of 7 to l0 lbs/2880 sq. ft.

5. The disposable surgical mask described in claim 1 characterized bythe barrier ply being made of tissue paper that has greater stiffnessthan either the inner or the outer facing and providing added stiffnessto the mask to hold the mid portion. of the mask away from a wearersface when the pleats are open and the mask is being worn.

6. The disposable surgical mask described in claim 1 characterized bythe barrier ply being made of tissue paper that has greater wet strengththan the inner facing to prevent wet-out of the mask by the breadth ofthe wearer 7. The disposable surgical mask described in claim 1characterized by the barrier ply being made of tissue paper that liesagainst the filter and that stiffens the mask so that the filter isreinforced against excessive flexing and thereby to reduce breakage ofportions of the filter material with resulting increase in the number ofspicules from the filter.

1. A disposable surgical mask comprising pleated plies of sheet materialwith the pleats extending across the face of the mask, binding coveringthe pleats at their ends, stitching through the binding and pleatedmaterial securing the pleats closed at the ends of the mask, the pliesincluding inner and outer facings for the mask, a ply of filter materialbehind the front facing, the filter being made of material from whichspicules of the filter become loosened during use of the mask, and a plyof barrier material between the filter and the inner facing of aporosity that stops spiclues of the filter from reaching the innerfacing during use of the mask, and the barrier ply being made of tissuepaper having a porosity of from 200 to 800 cu. ft./min (GurleyPermometer), a basis weight between 7 and 10 lbs./2880 sq. ft. andcomprising at least 50% long fiber, and a wet strength of about 580(machine direction) and 200 (cross direction) gms./inch.
 2. Thedisposable surgical mask described in claim 1 characterized by theporosity being between 400 and 600 cu.ft./min.
 3. The disposablesurGical mask described in claim 1 characterized by the pleats extendinghorizontally across the mask and having overlaps that unfold to increasethe vertical width of the mask at its mid section more than between 50and 100% of the vertical width when the pleats are folded, and all ofthe plies being in contact with one another and similarly pleated. 4.The disposable surgical mask described in claim 3 characterized by thebarrier coat being made of tissue paper having a porosity between 400and 600 cu.ft/min. and a wet strength above 290 (machine direction) and100 (cross direction) grams/inch, and having a basis weight of 7 to 10lbs/2880 sq. ft.
 5. The disposable surgical mask described in claim 1characterized by the barrier ply being made of tissue paper that hasgreater stiffness than either the inner or the outer facing andproviding added stiffness to the mask to hold the mid portion of themask away from a wearer''s face when the pleats are open and the mask isbeing worn.
 6. The disposable surgical mask described in claim 1characterized by the barrier ply being made of tissue paper that hasgreater wet strength than the inner facing to prevent wet-out of themask by the breadth of the wearer.
 7. The disposable surgical maskdescribed in claim 1 characterized by the barrier ply being made oftissue paper that lies against the filter and that stiffens the mask sothat the filter is reinforced against excessive flexing and thereby toreduce breakage of portions of the filter material with resultingincrease in the number of spicules from the filter.